1. Field of the Invention
The present invention relates to a microscope. More particularly, this invention pertains to a lens turret assembly used in a microscope.
2. Description of the Related Art
Microscopes often have turrets with multiple objective lenses. The turret, by its rotation, provides selection of objective lenses at will. Also, microscopes are frequently equipped with multiples of different illuminators for observation. For example, some microscopical observations involve caged reagents. Caged reagents are ordinarily in an inert state. When exposed to intense ultraviolet light, though, cleavage occurs only in those areas exposed to light and the reagent is activated in that area. These caged reagents are administered to biological specimens for observation. By casting intense ultraviolet light only on specific areas of the observed specimen one wishes to see, the caged reagent is cleaved and activated in that area. Then specific light is cast on the observed specimen by an epi-fluorescent illuminator and the biological specimen is observed in a state of fluorescent illumination by a microscope.
In microscope observations where caged reagents, like those described above, are used, two kinds of illumination devices are needed; that is, an intense, epi-ultraviolet light illuminator that causes the caged reagent to cleave and become activated, and an epi-fluorescent illuminator that stimulates the observed specimen and renders it observable through fluorescent light. Thus, microscopes with an epi-fluorescent illuminator in the microscope base also need to add an epi-ultraviolet light illuminator, to cleave caged reagents, stacked in the optical axis direction.
Moreover, a photographic device like a CCD camera can be used in the upper part of a microscope barrel lens in order to render specimens observable by television cameras. In even more sophisticated microscopes, focal point detectors can be provided with auto-focus functions. Some focal point detectors are detachable from the microscope, while others are housed in the microscope. Japanese Laid Open Patent Report Hei 4-260015 discloses an example of a focal point detector having three photographic elements: one for the pre-focus position,another for the accurate focus position, and the other for the post-focus position. Furthermore, U.S. Pat. No. 3,721,827 discloses the detection of light from a specimen via a divided sensor. One half of the optical path in the detector is used to cast light, and the other half is used to receive light.
Additional illuminators, as mentioned above, require new space for microscopes commonly equipped with a single illuminator in microscope bases. Thus, problems arise for up-light microscopes because the addition of illuminators causes the eye point position to become too high, the original observing positioning to change, and the workability to become poor. For inverted microscopes, problems occur in that the stage level becomes too high and, as mentioned earlier, the workability becomes poor. Also, dimensional compatibility with auxiliary equipment, such as a micromanipulator, may be jeopardized when the stage level is charged.
Also, some microscopes have conversion mechanisms in the optical path of the illuminator in the microscope base to allow switching between the optical path of the illuminator and that of another illuminator. However, such devices are complex and costly. Moreover, when a microscope is provided with photographic devices, focal point detectors, and other such optical detectors, the microscope becomes large due to the space necessary for the devices.